1. Field of the Invention
The present invention relates to an image forming apparatus and, more particularly, to an image forming apparatus, which transfers images on an image-receiving medium.
2. Description of the Related Art
Generally, such image forming apparatus as copying machines, laser printers and the like have a developing device, which forms a toner image corresponding to an image information on an image carrier, a transfer device, which transfers a toner image on an image receiving medium and a fixing device, which fixes the toner image on the image receiving medium.
When forming an image on the image receiving medium by this image forming apparatus, image data are first formed on the image receiving medium as an electrostatic latent image. Then, a charged toner is supplied to the image carrier and forcing this toner to adhere to the electrostatic latent image, a toner image is formed.
Further, the toner image thus formed is transferred on the image receiving medium by utilizing the electrostatic action. The image receiving medium carrying the transferred toner image is conveyed to the fixing device, applied with pressure, heat, etc. and the toner image is fixed on the image receiving medium and thus, an image is formed thereon.
On many of such an image forming apparatus as described above, a conveyor guide is provided between the transfer device and the fixing device. This conveyor guide is a member to help an image receiving medium carrying an transferred toner image being conveyed from the transfer device to the fixing device and is arranged so that the image receiving medium is conveyed while sliding on this conveyor guide.
Accordingly, this conveyor guide is demanded not to impede an image receiving medium to move when guiding it to the fixing device. In other words, the conveyor guide is demanded to have less contact resistance with an image receiving medium. Further, because an image receiving medium and a toner moving on the conveyor guide are charged, if the conveyor guide is conductive, the charge retained on the image receiving medium and the toner flows into the conveyor guide and causes the disturbance of a toner image. Therefore, the contact portions of the conveyor guide, which contact with an image receiving medium, are required to be well insulated.
As a conveyor guide satisfying such the demand, a metallic plate is used, of which surface has a plurality of streak shaped projections and lubricated/coated film of Bakelite with a thickness of about 10 .mu.m formed.
According to this conveyor guide, an image receiving medium slides and moves on these streak-shaped projections. Therefore, the contact resistance of this conveyor guide with the image receiving medium is less and does not impede the image receiving medium to move when it is guided to the fixing device. Further, the lubricated/coated film of Bakelite, etc. is an insulator and therefore, the electric charge hardly flows to the conveyor guide from an image receiving medium and a toner.
However, when such a conveyor guide is used, there will be generated a problem that a toner image on an image receiving medium is disturbed in the streak shape along said projections. In other words, the polarity of the electrostatic charge generated when an image receiving medium moves while sliding on the insulating conveyor guide on which the lubricated/coated film of Bakelite, etc. is formed and the charged polarity of a toner image on an image receiving medium are inverse to each other. Therefore, the toner of the toner image is attracted by the electrostatic charge generated on the conveyor guide as if the toner is left with the movement of the image receiving medium and the toner image on the image receiving medium is thus disturbed.